1. Field of the Invention
The present invention relates to an electrically rewritable non-volatile semiconductor storage device and a method of manufacturing the same.
2. Description of the Related Art
Non-volatile semiconductor storage devices are configured by semiconductor layers with lamination structure including memory cell arrays. Generally, the semiconductor layers are provided with contact layers on their surfaces that are connected to conductive layers within the semiconductor layers. The contact layers are connected by wiring layers and contact plugs.
According to a trend in the non-volatile semiconductor storage devices, the number of bits tends to increase for the purpose of providing a larger amount of data to be written to one chip. This is achieved by shrinking the area occupied by the semiconductor layers. One example structure achieving such shrinkage in occupation area is described in, e.g., Japanese Patent Laid-Open No. 2006-128390.
However, the smaller the area occupied by the semiconductor layers, the more refined the contact layers required. This would more likely cause short circuits between contact plugs formed in a contact layer. That is, this may lead to a malfunction. On the contrary, while some measures are taken to solve this problem by decreasing the radius of contact plugs, these measures would result in reduction in an alignment margin for contact plugs and contact layers. In addition, the smaller radius of contact plugs, the more difficult it becomes to process them and the higher resistance provided therein.